1. Field of the Invention
The invention concerns an optically activatable semiconductor component with at least one light-sensitive surface area containing a PN junction, which is biased in a nonconducting direction when exposed to light. The invention particularly concerns light-ignitable thyristors, which have such a structure.
2. Description of the Prior Art
A light-ignitable thyristor is known for example from German-Austrian [DE-OS] No. 2,408,079. This known component consists of a main thyristor and an integrated auxiliary thyristor for the purpose of ignition amplification. The base zone on the anode side leads up to the surface of the cathode side by means of a narrow channel, such that the PN junction formed by this base zone and the base zone on the cathode side likewise borders directly on the surface of the cathode side. When the surface on the cathode side is irradiated with light, the auxiliary thyristor ignites first, which then causes ignition of the main thyristor.
To keep the light intensity necessary for ignition as low as possible, it has already been suggested that the light-sensitive PN junction exposed at the surface of the component be given a finger-formed structure, and to concentrate the current flowing along this PN junction to individual areas of the P base zone. The N emitter of an auxiliary thyristor is then placed in these areas.
The disadvantage of these structures lies in the fact that this surface geometry entails a considerable reduction in the blocking voltage due to curvature of the PN-junction near the surface (c.f. IEEE ED-22, pp. 910-916, 1975).